KR20030065291A - Optical fiber and planar waveguide for achieving a substantially uniform optical attenuation - Google Patents

Abstract

PURPOSE: An optical attenuator is provided, which includes an optical fiber having a core doped with a dopant absorbing a light in a fixed wavelength band, and the optical fiber and a planar waveguide are provided, which attenuate an optical signal constantly. CONSTITUTION: An optical fiber is for obtaining a constant optical attenuation and has a core layer(13) and a clad layer(12). The core layer is co-doped with at least more than one ion of the first metals whose absorption coefficient has a negative slope in a fixed wavelength band and at least more than one ion of the second metals whose absorption coefficient has a positive slope in the fixed wavelength band. The first metals are Fe, Cr, Mn and V. And the second metals are cobalt and nickel.

Description

OPTICAL FIBER AND PLANAR WAVEGUIDE FOR ACHIEVING A SUBSTANTIALLY UNIFORM OPTICAL ATTENUATION

The present invention relates to an optical attenuation optical fiber and planar waveguide for attenuating a received optical signal in an optical communication system.

Wavelength division multiplexing (WDM) has been developed in addition to time division multiplexing (TDM) due to explosive demand for data to be transmitted in optical communication. WDM can improve the signal transmission efficiency by transmitting optical signals with different wavelengths through one transmission line.

In the optical communication system, since signal loss occurs in proportion to the length of the optical fiber, the reception side that is present at a long distance receives a weak signal, which makes it difficult to receive the correct signal.

In order to solve this problem of signal loss, an amplification means for amplifying the optical signal is disposed between the transmitting side and the receiving side, and the transmitting side transmits a signal of high output in consideration of such signal loss. However, when a receiving apparatus such as an optical fiber amplifier is installed near the transmitting side generating a high output signal, the receiving apparatus may not accurately detect such a signal. Therefore, a method for attenuating the optical signal received at the front end of the receiver has been used. That is, the ferules are shifted from each other, a certain amount of light is counted at small intervals between the ferrules, the sizes of the fiber cores are different, or a filter is inserted between the ferrules.

However, filter-type optical attenuators have too small attenuation zones to precisely control the degree of absorption.

It is an object of the present invention to provide an optical attenuator comprising an optical fiber having a core doped with a dopant that absorbs light in a predetermined wavelength band.

Another object of the present invention is to provide an optical fiber for constantly attenuating an optical signal of a predetermined wavelength band.

Another object of the present invention is to provide a planar waveguide for uniformly attenuating an optical signal in a predetermined wavelength band.

According to one aspect of the present invention, an optical attenuation optical fiber for obtaining a substantially constant light attenuation comprises a core layer and a cladding layer, the core layer having a first light absorption coefficient having a negative slope in a predetermined wavelength band The light absorption coefficient is co-doped with at least one ion of the metal and at least one ion of the second metal having a positive slope in a specific wavelength band.

Preferably, the first metal is iron (Fe), chromium (Cr), manganese (Mn) and vanadium (V), and the second metal is cobalt (Co) and nickel (Ni).

According to another aspect of the present invention, an optical attenuation optical fiber for obtaining a substantially constant light attenuation having a core layer and a cladding layer is a core layer doped with a first metal ion having a negative slope of a light absorption coefficient in a predetermined wavelength band. And a second optical fiber having a core layer doped with a second metal ion having a positive slope in a light absorption coefficient in a predetermined wavelength band, wherein the second optical fiber is in series with the first optical fiber. (in series) are connected.

According to another aspect of the present invention, a planar waveguide for obtaining a substantially constant light attenuation comprises a core and a cladding layer, the core having at least one or more of the first metals having a negative slope with a light absorption coefficient in a predetermined wavelength band. The light absorption coefficient in the predetermined wavelength band is co-doped with at least one ion of the second metal having a positive slope.

Preferably, the first metal is iron, chromium, manganese and vanadium and the second metal is cobalt and nickel.

The above objects and other features of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings.

1 is a flow chart showing an optical fiber manufacturing process for optical attenuation according to the first embodiment of the present invention.

2a to 2d are cross-sectional views showing the metal ion doping process shown in FIG.

3A to 3C are cross-sectional views illustrating a manufacturing process of an optical attenuation optical fiber according to a second embodiment of the present invention.

4 to 7 are graphs showing light absorption characteristics of first metal ions according to wavelengths.

8 and 9 are graphs showing the light absorption characteristics of the second metal ion according to the wavelength.

10 is a graph showing the light absorption characteristics of the optical fiber doped with iron (Fe) according to the wavelength.

FIG. 11 is a graph showing light absorption characteristics of a cobalt-doped optical fiber according to wavelength. FIG.

12 and 13 are graphs showing the light attenuation characteristics of the iron and cobalt co-doped optical fiber.

14 is a graph showing the light attenuation characteristics according to the length of the iron and cobalt co-doped optical fiber.

FIG. 15 is a graph showing light attenuation characteristics when a first optical fiber doped with iron and a second optical fiber doped with cobalt are connected in series. FIG.

16 is a view showing a planar waveguide for optical attenuation according to a third embodiment of the present invention.

17A to 17F are sectional views showing the manufacturing process of the optical waveguide planar waveguide according to the third embodiment of the present invention.

1 is a flow chart illustrating a manufacturing process of an optical attenuating optical fiber for obtaining a substantially constant optical attenuation according to a first embodiment of the present invention, using modified chemical vapor deposition (MCVD).

First, the cladding layer is deposited inside the tube using SiCl ₄ , POCl _3, and CF ₄ (ST1), and the core layer is deposited using SiCl ₄ and GeCl ₄ (ST2).

Thereafter, the core layer is partially sintered and doped with a predetermined metal ion (ST3). The core layer is dried, sintered and oxidized (ST4).

Then, an optical fiber preform is obtained through a collapsing and sealing step (ST5, ST6), and finally, an optical fiber containing metal ions is produced through a drawing process (ST7).

Hereinafter, a process of doping the core layer with metal ions will be described with reference to FIGS. 2A to 2D.

First, as shown in FIGS. 2A to 2D, the cladding layer 12 and the core layer 13 are deposited inside the tube 11 (FIG. 2A), and then partially sintered to form a porous layer (FIG. 2B). .

Subsequently, after impregnating the solution 14 containing a predetermined amount of metal ions into the porous layer, the state is maintained for about 1 hour (Fig. 2C).

Thereafter, the solution 14 is discharged from the tube 11. At this time, some of the metal ions dissolved in the solution 14 remain in the porous core layer. That is, the core layer 13 is doped with metal ions (FIG. 2D).

In this case, the metal ion dissolved in the solution 14 includes at least one ion of a first metal such as iron, chromium, vanadium and manganese, at least one ion of a second metal such as cobalt and nickel, aluminum The first metal has a negative slope of the light absorption coefficient in the optical signal wavelength band, and the second metal has a positive slope of the light absorption coefficient in the optical signal wavelength band. Aluminum is used to prevent evaporation of metal ions during the high temperature collapsing step.

In this case, the molar ratio of the first metal ion, the second metal ion, and the aluminum is 1 to 3: 4 to 6: 1 to 3. Since the final molar ratio value may vary depending on the temperature and gas pressure of the process, the molar ratio should be determined within the highest and lowest limits.

Thus, the core portion is co-doped with a first metal ion and a second metal ion having a light absorption coefficient having a negative slope and a positive slope, respectively, in the optical signal wavelength band, so that the improved optical fiber is substantially constant in the input optical signal. It can be done.

On the other hand, the optical attenuation optical fiber for making a constant light attenuation may be obtained by connecting the first optical fiber doped with the first metal ion and the second optical fiber doped with the second metal ion in series. 3A to 3C show an optical fiber for making a constant light attenuation according to a second embodiment of the present invention.

3A shows a preform of a first optical fiber having a porous core layer 13 doped with a first metal ion 21, and FIG. 3B shows a second optical fiber having a porous core layer 13 doped with a second metal ion. Freeform. In the second embodiment, as shown in Fig. 3C, the first optical fiber 23 doped with the first metal ion 21 and the second optical fiber 24 doped with the second metal ion 22 are transmission paths. It is interposed separately between the general optical fiber 25 forming a.

In the case where the first optical fiber is doped with 0.125 mol of iron ions and the second optical fiber is doped with 0.3 mol of cobalt ions, the length ratio of the first optical fiber L1 and the second optical fiber L2 is L1: L2 = 1: 2.

Of course, as described above, the core layer is co-doped with aluminum, and the molar ratio of the first metal ion to the second metal ion to aluminum is 1 to 3: 4 to 6: 1 to 3.

Hereinafter, the light absorption coefficients of the first and second metal ions will be described with reference to FIGS. 4 to 15.

4 to 7 show light absorption coefficients of the first metal ion which varies with wavelength.

Figure 4 shows the light absorption coefficient according to the wavelength in the quartz glass containing iron, having a negative slope in the wavelength band of about 1100nm to 1900nm.

Figure 5 shows the light absorption coefficient according to the wavelength in the quartz glass containing vanadium, and has a negative slope in the wavelength band of about 700nm to 1800nm.

Figure 6 shows the light absorption coefficient according to the wavelength in the quartz glass containing chromium, and has a negative slope in the wavelength band of about 600nm to 1600nm.

FIG. 7 shows light absorption coefficient according to wavelength in quartz glass containing manganese, and has a negative slope in the wavelength band of about 450 nm to 1600 nm.

That is, the first metal ions such as iron, vanadium, chromium, and manganese have a negative slope in the light absorption coefficient in a predetermined wavelength band of about 1100 nm to 1600 nm as shown in FIGS. 4 to 7.

In addition, the light absorption coefficients of the second metal ions are shown in FIGS. 8 and 9. 8 shows the light absorption coefficient according to the wavelength of quartz glass containing cobalt, and has a positive slope in the wavelength band of about 900 nm to 1800 nm.

FIG. 9 shows light absorption coefficient according to wavelength in quartz glass containing nickel, and has a positive slope in the wavelength band of about 1000 nm to 1600 nm.

That is, the second metal ions such as cobalt and nickel have a positive slope in the light absorption coefficient in a predetermined wavelength band of about 1100 nm to 1600 nm, as shown in FIGS. 8 and 9.

On the other hand, Figure 10 shows the light absorption coefficient in the optical fiber doped with iron ions, and has a negative slope in the wavelength band of about 1150nm to 1650nm.

11 shows a light absorption coefficient of the optical fiber doped with cobalt ions, and has a positive slope in the wavelength band of about 900 nm to 1650 nm.

That is, in comparison with FIGS. 4 and 10 and FIGS. 8 and 11, the light absorption coefficient has a negative slope at the wavelength of the optical signal transmission band of approximately 1200 nm to 1600 nm although there is a slight difference.

12 and 13 show the light attenuation characteristics of the optical fiber according to the first embodiment of the present invention in which iron ions, cobalt ions and aluminum ions are co-doped in a predetermined molar ratio, for example, 1: 4.4: 1.6.

FIG. 12 shows light attenuation characteristics of an optical fiber doped with iron and cobalt using a white light source as input light, and the light attenuation deviation is approximately ± 0.4 dB in a wavelength band of 1200 nm to 1600 nm. In this case, the length of the optical fiber was 1 mm.

FIG. 13 shows optical attenuation characteristics of an optical fiber doped with iron and cobalt using a broadband light source as a input light. The optical attenuation deviation is approximately ± 1 dB in the wavelength band of 1450 nm to 1600 nm.

As the optical attenuation level changes according to the length of the optical fiber, FIG. 14 shows the optical attenuation characteristic according to the optical fiber length doped with iron ions and cobalt ions when the input wavelength is 1550 nm.

In this case, since the attenuation rate is about 5 dB per 1 mm of the fiber co-doped with iron ions and cobalt ions, the longer the length of the optical fiber, the higher the light attenuation level.

On the other hand, Figure 15 shows the optical attenuation characteristics of the optical fiber according to the second embodiment of the present invention, 5cm of the first optical fiber doped with iron ions and 10cm of the second optical fiber doped with cobalt ions are connected in series. In this case, the molar ratio of iron ions to cobalt ions is 0.125: 0.3. This shows a substantially constant light attenuation in the wavelength range of 1300 nm to 1600 nm.

Therefore, according to the present invention, a core is formed of one ion of one of the first metals having a negative slope with a light absorption coefficient and one ion of a second metal having a positive slope with a light absorption coefficient in a predetermined optical signal wavelength band. By co-doping the layer a constant optical attenuation optical fiber can be provided. In particular, the co-dopant pairs described above include iron and cobalt ions, chromium ions and cobalt ions, manganese and cobalt ions, iron and nickel ions, vanadium and nickel ions, chromium and nickel ions, manganese and nickel ions. And the like. This may be provided by connecting a first optical fiber doped with ions of one of the first metals and a second optical fiber doped with ions of one of the second metals in series.

While it has been shown and described that it is to be considered a preferred embodiment of the invention, it is to be understood that the invention is not limited to the specific embodiments and that various changes, modifications and equivalents may be substituted without departing from the scope of the invention. Those skilled in the art will understand.

For example, the core layer may be co-doped with a mixture of at least two of the first metals including iron ions, vanadium ions, chromium ions, and manganese ions in a predetermined ratio, and a mixture of cobalt and nickel in a predetermined ratio. It is possible to manufacture a fiber for constant light attenuation.

Otherwise, constant optical attenuation by connecting in series a first optical fiber doped with a mixture of at least two of the first metals in a predetermined ratio and a second optical fiber doped with a mixture of at least two of the second metals in a predetermined ratio. The optical fiber can be obtained.

In addition, the optical attenuator can be configured using the optical attenuation optical fiber according to the embodiment.

Further, the above-described improved concept can equally be applied to planar waveguides for light attenuation. That is, by co-doping the core with the dopant, a planar waveguide for obtaining a substantially constant light attenuation can be obtained.

16 shows a planar waveguide for optical attenuation according to a third embodiment of the present invention. The improved planar waveguide for light attenuation has a core 33 co-doped with at least one ion of the first metal and at least one or two ions of the second metal. Denoted at 32 is a cladding layer and at 31 is a Si substrate.

The planar waveguide for the optical attenuation of the present invention may have a plurality of cores. As a result, the planar waveguide of the present invention may have a plurality of waveguides composed of cores and a cladding layer surrounding the cores.

17A to 17F are cross-sectional views illustrating a manufacturing process of a planar waveguide for optical attenuation according to a third embodiment of the present invention.

First, as shown in FIG. 17A, a buffer cladding layer 32a is formed on the Si substrate 31 using the flame hydrolysis deposition method (FHD). The buffer cladding layer 32a may be SiO ₂ -P ₂ O ₅ , SiO ₂ -B ₂ O _3, or SiO ₂ -P ₂ O ₅ -B ₂ O ₃ .

Then, as shown in Fig. 17B, the core layer 33 is formed on the buffer cladding layer 32a using the FHD method. The core layer may be SiO ₂ -GeO ₂ -P ₂ O ₅ , SiO ₂ -GeO ₂ -B ₂ O _3, or SiO ₂ -GeO ₂ -P ₂ O ₅ -B ₂ O ₃ .

Thereafter, as shown in Fig. 17C, the core layer 33 is partially sintered to form the porous layer 33a.

Thereafter, the porous layer 33a is doped with metal ions to form a doped porous layer 33b as shown in Fig. 17D. The doping process includes impregnating a porous layer in a solution containing a predetermined amount of metal ions, holding for approximately one hour, and drying the porous layer. In this case, the metal ions dissolved in the solution include at least one or more ions of a first metal such as iron, chromium, vanadium and manganese, at least one or more ions of a second metal such as cobalt and nickel, and aluminum ions. The first metal has a negative slope in the light absorption coefficient in the optical signal wavelength band and the second metal has a positive slope in the optical signal wavelength band. In addition, the molar ratio of a 1st metal ion, a 2nd metal ion, and aluminum is 1-3: 4-6: 1-3.

Thereafter, as shown in FIG. 17E, the core 33c is formed by photolithography and an etching process.

Then, as shown in Fig. 17F, the over cladding layer 32b is formed on the core 33c and the buffer cladding layer 32a by the FHD method, and as a result, the cladding layer 32 is formed. . The over cladding layer may be SiO ₂ -P ₂ O ₅ or SiO ₂ -P ₂ O ₅ -B ₂ O ₃ .

As a result, the light absorption coefficient of the improved planar waveguide core for optical attenuation can have a constant attenuation for the input optical signal in the optical signal wavelength band.

As described above, according to the present invention, the light absorption coefficient has at least one ion of the first metal in which the light absorption coefficient has a negative slope, and the light absorption coefficient has a positive slope in the predetermined optical signal wavelength band. By co-doping the core layer with at least one ion of the second metal, a constant optical attenuation optical fiber and planar waveguide are provided by the core. In particular, the first metals are iron, chromium, manganese and vanadium and the second metals are nickel and cobalt. In addition, an optical fiber for constant light attenuation is provided by connecting a first optical fiber doped with at least one ion of the above-described first metal and a second optical fiber doped with at least one of the above-mentioned second metal in series.

Claims (8)

An optical fiber for obtaining a substantially constant light attenuation having a core layer and a cladding layer, The core layer includes at least one ion of the first metal having a negative slope with a light absorption coefficient in a predetermined wavelength band and at least one ion of the second metal having a positive slope with a light absorption coefficient in the predetermined wavelength band. Co-doped optical fiber. The optical fiber of claim 1, wherein the first metal is iron, chromium, manganese, and vanadium, and the second metal is cobalt and nickel. The optical fiber of claim 1, wherein the core layer is co-doped with aluminum to obtain a substantially constant light attenuation. An optical fiber for obtaining a substantially constant light attenuation having a core layer and a cladding layer, the optical fiber comprising: A first optical fiber having a core layer doped with a first metal ion having a negative light absorption coefficient in a predetermined wavelength band; And And a second optical fiber having a core layer doped with a second metal ion having a positive slope in the light absorption coefficient in the predetermined wavelength band, and connected in series with the first optical fiber. The optical fiber of claim 4, wherein the first metal comprises at least one of iron, vanadium, chromium, and manganese, and the second metal comprises at least one or both of cobalt and nickel. A planar waveguide for obtaining a substantially constant light attenuation having a core layer and a cladding layer, the core layer having at least one ion of a first metal having a negative slope of a light absorption coefficient in a predetermined wavelength band and in the predetermined wavelength band. A planar waveguide co-doped with ions of at least one of the second metals whose light absorption coefficient has a positive slope. 7. The planar waveguide of claim 6, wherein the first metal is iron, chromium, manganese and vanadium, and the second metal is cobalt and nickel. 7. The planar waveguide of claim 6, wherein the core is co-doped with aluminum to achieve a substantially constant light attenuation.